Process for the manufacture of a decorative laminate

ABSTRACT

A process for the manufacture of a decorative board, which board, on its upper surface includes a decorative layer and a wear layer of cellulose and thermosetting amino resin. A decorative layer and wear layer is applied as a surface layer on a base layer and bonded thereto by pressing under elevated temperature and pressure in a laminate press. The wear layer, the decor layer and the base layer are arranged to form a stack of layers. The stack of layers are fed into a laminate press and pressed therein under heat and pressure where at least the upper surface becomes heated. The decorative board is acquired from the laminate press whereupon a forced cooling of the decorative board is initiated in order to bring the surface temperature of the decorative board down.

The present invention relates to a process for the manufacture of a decorative thermosetting laminate by means of a laminate press.

Products coated with thermosetting laminates are frequent today. They are foremost used where the demand for abrasion resistance is high, but also where resistance towards different chemicals and moisture is required. As an example of such products floors, floor beadings, table tops, work tops and wall panels can be mentioned.

The thermosetting laminate most often consists of a carrying base with a decor sheet and one or more wear layers placed closest to the surface. The decor sheet can be provided with a desired decor or pattern. The most frequent patterns usually represent the image of different kinds of wood, or minerals such as marble or granite. The surface of the laminate can be provided with a structure during the laminating procedure which will make the decor more realistic. The most common way of achieving such a laminate is by first manufacturing the thermosetting laminate of a number of paper layers impregnated with melamine formaldehyde resin and then to glue this thermosetting laminate onto a core of for example fibre board or particle board. It is also known to feed a few melamine formaldehyde impregnated paper webs together with sheets of particle or fibre board through a continuous laminate press. The problem is that the laminate will change format somewhat which will cause problems with warping due to changes in moisture content. The same problem occurs in both continuous and discontinuous processes.

According to the present invention the above mentioned problems have been solved and a process for manufacturing a laminate including a conditioning procedure has been achieved. Accordingly the present invention relates to a process for the manufacture of a decorative board, which board, on its upper surface includes a decorative layer and a wear layer, said decorative layer and wear layer comprise cellulose and thermosetting amino resin. The decorative layer and wear layer is applied as a surface layer on a base layer and bonded thereto by pressing under elevated temperature and pressure in a laminate press. The wear layer, the decor layer and the base layer are arranged to form a stack of layers. The stack of layers is then fed into a laminate press and pressed therein under increased pressure and increased temperature so that the different layers are bonded to form a unit, through which process, at least the upper surface becomes heated. The decorative board is then acquired from the laminate press whereupon a forced cooling of the decorative board is initiated in order to bring the surface temperature of the decorative board down. The cooling process is started as soon as possible after the lamination procedure in order to prevent the heat to dissipate into the base layer. The heat will lower the moisture content of the base layer to a level lower than the equilibrium moisture content during normal use. The base layer will of course absorb moisture so that equilibrium is eventually achieved, but during this process undesired warping of the decorative board may occur.

The base layer is in preferred embodiments constituted of a particle board, a medium density fibre board or a high density fibre board with a thickness in the range 3-30 mm.

The base layer is preconditioned to a predetermined temperature prior to the lamination process.

The cooling is preferably achieved by means of convection cooling by blowing an air stream over the surface of the decorative board. The air in the air stream is suitably conditioned to a specific moisture content range and a specific temperature range. The cooling process is suitably divided into a two stage process, the first stage being a forced narrow high pressure air stream blown over the surface of the decorative board as soon as possible after the lamination procedure, followed by stage two, being a slower cooling process where the air used for cooling is conditioned to a specific temperature range and moisture content. The drying of the laminate below equilibrium moisture levels for normal use will hereby be radically limited and one of the reasons to problems with warping of finished products can be limited to a controllable level.

According to one embodiment of the invention the pressure in the laminate press is in the range 5-90 Bar, preferably 15-70 Bar, while the temperature is in the range 140-260° C. preferably 160-200° C.

According to one embodiment of the invention the decorative boards comprises a wear layer which is constituted by at least one web or sheet of cellulose impregnated with melamine formaldehyde resin. The wear layer may also include small hard particles of, for example, silicon oxide, silicon carbide or aluminium oxide. The small hard particles may for example be incorporated in the pulp during manufacturing of the cellulose web, sprinkled on the wet lacquer during the impregnation procedure or incorporated in the lacquer used for impregnation. Also the decor sheet is suitably made of cellulose which is impregnated with melamine formaldehyde resin.

The base layer is suitably preconditioned to a predetermined moisture content and temperature prior to being provided with a decor sheet.

Also the decor sheet and the wear layer is suitably also preconditioned to a predetermined moisture content and temperature prior to being applied on the base layer.

The decorative layer is suitably provided with a surface structure. This is suitably achieved by means of any known technique of embossing. 

1. A process for the manufacture of a decorative board, which board, on its upper surface includes a decorative layer and a wear layer, said decorative layer and wear layer comprise cellulose and thermosetting amino resin wherein a decorative layer and wear layer is applied as a surface layer on a base layer and bonded thereto by pressing under elevated temperature and pressure in a laminate press wherein: a) the wear layer, the decor layer and the base layer are arranged to form a stack of layers whereupon, b) the stack of layers are fed into a laminate press and pressed therein under increased pressure and increased temperature so that the different layers are bonded to form a unit, through which process, at least the upper surface becomes heated, whereupon, c) the decorative board is acquired from the laminate press whereupon a forced cooling of the decorative board is initiated in order to bring the surface temperature of the decorative board down.
 2. A process according to claim 1, wherein the base layer is constituted of a particle board with a thickness in the range 3-30 mm.
 3. A process according to claim 1, wherein the base layer is constituted of a medium density fibre board with a thickness in the range 3-30 mm.
 4. A process according to claim 1, wherein the base layer is constituted of a high density fibre board with a thickness in the range 3-30 mm.
 5. A process according to claim 2, wherein the base layer is preconditioned to a predetermined temperature prior to the lamination process.
 6. A process according to claim 1, wherein the cooling is achieved by means of convection cooling by blowing an air stream over the surface of the decorative board.
 7. A process according to claim 6, wherein the air in the air stream is conditioned to a specific moisture content range.
 8. A process according to claim 6, wherein the air in the air stream has a specific temperature range.
 9. A process according to claim 6, wherein the cooling is a two stage process, the first stage being a forced narrow high pressure air stream blown over the surface of the decorative board as soon as possible after the lamination procedure followed by stage two, being a slower cooling process where the air is conditioned to a specific temperature range and moisture content.
 10. A process according to claim 1, wherein the pressure in the laminate press is in the range 5-90 Bar, while the temperature is in the range 140-260° C.
 11. The process according to claim 3, wherein the base layer is preconditioned to a predetermined temperature prior to the lamination process.
 12. The process according to claim 4, wherein the base layer is preconditioned to a predetermined temperature prior to the lamination process.
 13. The process according to claim 1, wherein the pressure in the laminate press is in the range 15-70 Bar, while the temperature is in the range 160-200° C.
 14. The process according to claim 1, wherein the pressure in the laminate press is in the range of 15-70 Bar.
 15. The process according to claim 1, wherein the temperature is in the range of 160-200° C. 